mentioned in issue #696 (closed)

As @vivekkde noticed

it is counting both audio and video track. Like if their are 2 audio tracks and 8 video tracks it will increase the size as total count is 10.

Something like this solves it:

    function getAudioTracksCount(){
        var audioCount = 0;
        for (var i = 0; i < trackHeaderRepeater.count; i++) {
            if(trackHeaderRepeater.itemAt(i).isAudio) {
                audioCount++;
            }
        }
        return audioCount;
    }

property int trackTagWidth: fontMetrics.boundingRect("M").width * ((getAudioTracksCount() > 9) || (trackHeaderRepeater.count - getAudioTracksCount() > 9)  ? 3 : 2)

@jlskuz yes, as soon as there are more than 10 tracks are added the label gets enlarged.

I think the correct term should be:
if there are more than 10 videoTracks
or more than 10 audioTracks
then the label should be enlarged